As metal should be, it's complex enough to demand your full attention to appreciate it, but not so unnecessarily scattered or avant-garde that you won't remember any of it or want to listen to it again. (I'm on my third listen of both songs below as I finish this post.) That is to say, it bears the mark of true talent of being able to create tension and violate expectation within a still-familiar framework. For example, they create a lot of rhythmic tension by placing a sixteenth note in a riff where you don't expect it, rather than constantly resorting to grating polyrhythms or strange meters. Listen to the outro of Organic Hallucinosis.
Spheres of Madness, Nihility (2002)
In Spheres above I particularly like the riff that begins at 2:30. Not what you would have predicted anyone would put there.
A final comment: highly technical and innovative bands also tend to come out of the starting gate that way, or at least tend to write that way as soon as they're proficient on their instruments, so it's interesting that Decapitated follow this pattern. (Is there any band that gets technical for the first time later in their careers?) I'm glad I discovered them now. They have a new record as of two weeks ago, Carnival is Forever. Support good metal.